Priorities for newbies?

[Rawrz]

Make sure you get your cross class skills, ideally before you hit 40. Leveling them is like leveling your main class for their skills.

If going SCH:

Raise your Thaumaturge to 26 for Swiftcast. Probably the most important cross in the game, behind Protect maybe.
Raise your Conjurer to 34 for Stoneskin on top of all the skills below 15. It's situational but works well prepull.

For SMN (Which I'm guessing you're going) :

Again, level Thaumaturge to 26 for Swiftcast.
Raise Archer to at least 4 for Raging Strikes and later on to 34 for Hawk's Eye (100% accuracy) and Quelling Strikes (Reduced aggro gained).

Have fun :O